1. Field of the Invention
The present invention relates to a switch controlling circuit, a switch circuit utilizing the switch controlling circuit, and methods thereof, and particularly relates to a switch controlling circuit that can avoid rush current, a switch circuit utilizing the switch controlling circuit, and methods thereof.
2. Description of the Prior Art
FIG. 1 is a circuit diagram illustrating a prior art switch circuit (or called a power switch circuit) 100. As shown in FIG. 1, the switch circuit 100 includes a plurality of switch units 101, 103, and 105 and is located between a supply voltage level Vcc and a logic circuit 107. Such circuit structure is called a header type switch circuit, and the transistor in each switching unit is a P-MOSFET. The switch circuit 100 turns on or off, to provide a current to the logic circuit 107.
FIG. 2 is a circuit diagram illustrating another prior art switch circuit 200. As shown in FIG. 2, the switch circuit 200 includes a plurality of switch units 201, 203, and 205 and is located between a voltage level VGND and a logic circuit 207. Such circuit structure is called a footer type switch circuit, and the transistor in each switching unit is an N-MOSFET. The switch circuit 200 turns on or off, to sink a current from the logic circuit 207.
However, both of the switch circuits include the same disadvantages: the switch units thereof will turn on at the same time. Therefore, the power supply will charge the decoupling capacitance in the logic circuit. Due to the decoupling capacitance does not have any charges before power switch turns on so that the decoupling capacitance will suffer a large instantaneous current (or called a rush current) when the switch units turn on simultaneously. The large instantaneous current may causes large IR drop and may causes function errors in logic circuits that are in another power domain.